Crank hard to turn

[rippedbx]

05 YZ250

just got a new bottom end and just assembled the cases. Now the crank is pretty hard to turn by hand. Is this normal for a fresh crank? I have to use significant effort to turn it from the rod.

one side of the case is off another bike, but same part number of course.

new main bearings and seals

new wiseco crank

[Vietze]

Yes, new seals are sometimes damn tight.

If you reassembled it properly and did a light hammer stroke on both ends of the crank it should be fine.

Just to be on the safe side doublecheck everything. also the clutchside etc.

I did a YZ 125 engine some month ago and while a putting everything together the shiftshaft got lose and got tweaked between clutchbasket and case...

[arnego2]

Depending on how the bearing were pressed in I'd say. There is a some resistance but it should still be easy to turn the crank.

[rippedbx]

well i hammered the bearings in by placing an old one over them and then a large socket over that. they turned easily once they were seated.

also I realized that I forgot to grease one of the seals...

but it does take quite a bit of force to turn the crank. something that just "breaks in" over time?

[BRM]

Some thing is wrong, sounds like the bearings are binding. How did you install the crank into the bearings?

[USED YZ426F]

Um. Something is definitely not right with your bottom end.

New seals would cause a noticable drag, but the whole assembly should still be pretty easy to spin by hand.

This is not something that will get better over time. You have something binding somewhere and will cause permanent damage if you don't fix it now.

Also, pounding the crank bearings in is never a good idea. Too much chance of either damaging them or getting them in slightly crooked. You should have heated the case halves in the oven (300 degrees for 30 minutes worked for me) and put the bearings in the freezer overnight. Then take the frozen bearing and simply drop it into the case half. I had to tap them each very lightly with a hammer and large socket, I just barely tapped on them.

[JS264]

How did you put the crank into the half/pull the cases together?

[rippedbx]

thanks for the replies!

I installed the crank into the left side using a makeshift installer and a bolt. Once it was installed in that side it turned easily and was perfectly straight.

When I put the two case halves together, i used the case bolts and tightened them equally on all sides. The crank would make a squeaking/popping sound by the right main bearing every time I tightened the case bolts, but I was assuming that was normal.

The transmission shafts turn just fine.

So I'm thinking the right main bearing isn't in right. I'm gonna start splitting it now...

[GMO397]

Never pull the cases together by the case bolts.

I would suggest re-splitting the bottom end and redoing it.

I'm anal, so I would throw new main bearings in, but that's me.

You need to pull the cases together by pulling the crank and pushing on the inner race of the main bearing.

This allows the cases to come together without any binding or damaging of the main bearings.

Heat and cold, or a puller work best.

I made my own puller. I used a peice of PVC pipe cut square on the ends. The peice needs to be the same size as the inner race of the main bearing. Put this over the exnd of the crank, against the main bearing. Then a large washer over the end of the pvc with a nut on the end of the crank against the washer. Tighten this nut and it will pull the cases together.

[tim512]

+1 re-split

You need to pull the crank into one side of the cases, then put the cases together and pull the crank into the other side. Only then is everything even. The bolts are there to hold together the cases, not pull them together..

I just split my cases recently, and when I first went to put them back together I stuffed it up and had to re-split, scrape all the liquid gasket off, and do it all again. It was painful, but I'm glad I did it.

[scalejockey]

Man....a little surprised on all these answers.

Pop the end of the crank with a deadblow rubber mallet. It will seat the bearings.

Iv'e been splitting cases for 35 years. This works!

I should of added,,, one pop should do it if anymore,split them and check clearance.

Edited November 4, 2011 by scalejockey

[adam728]

I'm on board with the "split it again" group. Pulling it together with the case halves leaves a lot of preload on the bearings and makes it tight. I'm sure 99% of the time a pop with a dead blow hammer will free it up without issue, but to me it's not worth the risk of knocking the crank out of true. I worked in a shop and rebuilt crankshafts, and was always amazed how little of a strike with a dead blow could move cranks when truing them.

[rippedbx]

K I resplit them. When the crank was in the right side, it was still very hard to turn. The crank wasn't touching any part of the case. As I was pulling the crank out of the main bearing, even when it was half way out, it was still pretty hard to turn. I was under the impression that the right side bearing slips over the crankshaft fairly easily?... Was the crank's tight fit putting pressure on the ball bearings? The bearing spins easily in the case with the crank removed.

And it wasn't anything to do with the seal.

I just removed the bearing. I'm probably going to freeze the bearing tonight and put the case in the oven and seat it again the right way. I probably shouldn't reuse that bearing because i had to pound it out, but I don't want to wait for more bearings to come in.

Any other suggestions?

[BRM]

Never pull the cases together by the case bolts.

I would suggest re-splitting the bottom end and redoing it.

I'm anal, so I would throw new main bearings in, but that's me.

You need to pull the cases together by pulling the crank and pushing on the inner race of the main bearing.

This allows the cases to come together without any binding or damaging of the main bearings.

Heat and cold, or a puller work best.

I made my own puller. I used a peice of PVC pipe cut square on the ends. The peice needs to be the same size as the inner race of the main bearing. Put this over the exnd of the crank, against the main bearing. Then a large washer over the end of the pvc with a nut on the end of the crank against the washer. Tighten this nut and it will pull the cases together.

Reinstall the crank like the aforementioned.

If you have pounded the bearings out then get some new ones from the local bearing shop.

If not that is you perogative.

[rippedbx]

Reusing the main bearing... I know, I know...

Wait, they sell these types of bearings at "bearing shops"? I was under the impression that they are dirt bike specific...

So I froze the main bearing and threw the Right crankcase in the oven and the bearing dropped right in. Put it all back together and it turns great.

I assume the problem was that the bearing wasn't seated correctly in the crankcase before.

Thanks everybody!

[argclh6670]

Yeah bud, I just redid the bottom on my sons cr. And what I did was googled bottom end rebuild on a 2s. Rocky mountain has a series of good vids showing how to do it. Or, start asking question on how To! Do you have manual, there is section on this in the manual. You don't need all the spceial tools but does make it easier. After I did my cr, there was considerable amount of drag on new crank assembly which madexit alil hard to spin by hand.